Skip building on TruffleRuby

Rakefile

@@ -17,8 +17,13 @@ namespace :version do
   end
 end
 
-require 'rake/extensiontask'
-Rake::ExtensionTask.new("fiddle")
-Rake::ExtensionTask.new("-test-/memory_view")
+
+if RUBY_ENGINE == 'ruby'
+  require 'rake/extensiontask'
+  Rake::ExtensionTask.new("fiddle")
+  Rake::ExtensionTask.new("-test-/memory_view")
+else
+  task :compile
+end
 
 task :default => [:compile, :test]

ext/fiddle/extconf.rb

@@ -1,4 +1,10 @@
 # frozen_string_literal: true
+
+if RUBY_ENGINE != 'ruby'
+  File.write('Makefile', dummy_makefile("").join)
+  return
+end
+
 require 'mkmf'
 
 # :stopdoc:

lib/fiddle.rb

@@ -1,6 +1,12 @@
 # frozen_string_literal: true
 
-require 'fiddle.so'
+if RUBY_ENGINE == "ruby"
+  require 'fiddle.so'
+else
+  $LOAD_PATH.delete(__dir__)
+  require 'fiddle' # load from stdlib
+end
+
 require 'fiddle/closure'
 require 'fiddle/function'
 require 'fiddle/version'

test/run.rb

@@ -3,8 +3,8 @@
 $VERBOSE = true
 
 source_dir = "#{__dir__}/.."
-$LOAD_PATH.unshift("#{source_dir}/test")
-$LOAD_PATH.unshift("#{source_dir}/lib")
+$LOAD_PATH.unshift(File.expand_path("#{source_dir}/test"))
+$LOAD_PATH.unshift(File.expand_path("#{source_dir}/lib"))
 
 build_dir = Dir.pwd
 if File.exist?("#{build_dir}/fiddle.so")